If we assume that T1 = T2 (it probably won't, but it is close enough), then
P1V1 = P2V2

P1 = 125 psi plus 15 psi = 140 psi
P2 = 15 psi

Therefore V2 is approximately 10 times V1.

So the air in your tank is going to occupy a space equal to 10 times the size of your tank. If it completely fails, that is a pretty big radius for the shrapnel to move.

If it fails locally, the air stream can cut like a knife. Remember how you were always told not to put a blow gun at your skin?

If you are capable of putting in ASME Code quality welds, cut the bottom head off. Chances are you will find the shell and the top head in pretty good condition. If not, you have nothing. If the damage is localized on the bottom head, cut out a circular hole which removes all of the damage and double butt weld in a patch. If the area is larger than about 1/4th the head diameter, buy a new head. Weld the head back on the shell. Fill the tank with water and pressurize it to 190 psi. Drain the tank and you are good to go.

Not sure what your time and materials are worth to you, but a new tanks seems the most economical way to go here.

If your good with the welder, just fix the hole. These tanks don't "explode" like some people imply. They just don't know any better and compressed air scares them.

Quote:

Originally Posted by Handkind

I agree with 65GTO. Compressors are not an explosion hazard unless they had an excess amount of oil built up inside. Even at that it would take some time for the thing to blow if it is depleted of air and that much oil would be from a VERY old tank.

That is 100$ USDA certified Bull&#!^!

Tanks most certainly do explode from structural failure and attempting to repair one by welding is usually the cause. NEVER, EVER weld on an air tank! In the first place if it has reached the point where it is already leaking then it has reached the end on it's service life and it would be dangerous to continue using it no matter whether the hole was "fixed" or not so the quality of the weld or skill of the welder does not have a darn thing to do with it. I have personally seen the results of two tank explosions and had safety bulletins on many more during the many years I serviced these things and I can tell you for a fact that the only myth here is saying they don't explode. I hate to be so blunt but peoples' very lives could be at stake on this one and to recommend to someone to weld on a tank is being extremely reckless.

In 1986 a 40 gallon tank that had been welded on a service truck exploded and peeled the top of a DM800 Mack truck open like a sardine can! Another one blew out and took out a block wall in a garage leaving a hole big enough to drive a pickup truck through! These two I personally saw and both tanks had been "repaired" by welding, the one in the garage didn't hurt anyone but the one with on the truck nearly killed a mechanic working near it. Fellas welding on an air compressor tank is extremely dangerous and it is nothing short of just plain stupid to say it is not!

But anyways, I think you should read the entire thread before blasting away.

Also another thing to take into account is Regulators. There was been little talk on regulators and what it means if one fails. Will the pump burn out before pressure builds too high? Sounds like another topic for discussion.

Some people in this world shouldn't even be around ladders. I have a feeling more people have died from falling off ladders as apposed to being injured by compressors. I tried looking up compressor related injuries but couldn't find any statistics. I do however have a sneaky feeling that more people die from choking on bar peanuts, quite frankly. Even spoons can kill people.

If you can't use your brain, you shouldn't be around an air compressor.

It does take someone who knows what they are doing.

Can someone safely repair an air compressor? Yes. But only if the previous line is taken into account.

Also, do you know what an air compressor tank is? Sheet metal welded together.

Oldred is right about repairing compressor tanks, after the tank starts leaking it should be scrapped. If someone trys to make any repairs the tank has to be hydrostaticly tested. And that pressure is 130% to 150% of the working pressure. Many times a tank or pressure vessel may be repaired because it is too costly or not feasible to replace it. But it has to be tested. Also age of the tank is of major concern when dealing with tanks.

On a small compressor it is wise to replace rather than repair. It's not worth your life.
Reference Mythbusters episode about the waterheater explosions.

But anyways, I think you should read the entire thread before blasting away.

Also another thing to take into account is Regulators. There was been little talk on regulators and what it means if one fails. Will the pump burn out before pressure builds too high? Sounds like another topic for discussion.

Some people in this world shouldn't even be around ladders. I have a feeling more people have died from falling off ladders as apposed to being injured by compressors. I tried looking up compressor related injuries but couldn't find any statistics. I do however have a sneaky feeling that more people die from choking on bar peanuts, quite frankly. Even spoons can kill people.

If you can't use your brain, you shouldn't be around an air compressor.

It does take someone who knows what they are doing.

Can someone safely repair an air compressor? Yes. But only if the previous line is taken into account.

Also, do you know what an air compressor tank is? Sheet metal welded together.

[End]

Read the whole thing? Sure I did and what I read was advice to weld on this old tank which is extremely dangerous whether you believe that or not! The statement was clearly made that tanks do NOT explode which they in fact certainly do! Argue to the contrary if you like but there are many examples of them doing just that. Like I said I have personally seen two and have seen several safety bulletins of more examples, the vast majority being old and/or repaired tanks. Darn right I came on strong because that kind of advice can get people hurt or killed and there should be no misunderstanding of just how dangerous this practice is, I am speaking from many years of dealing with these things and I know first hand just how dangerous it is.

The fact that tanks are welded together means nothing because these are welded using new metal while a cracked/leaking tank is rusty and/or fatigued. "Can someone safely repair an air compressor"? I assume you mean tank? then no you can not because even if the crack/hole is "repaired" you still have a dangerous, weak, rusty and fatigued tank which almost certainly will be damaged even more in the attempt to weld it. When a tank has reached the end of it's service life then a fatigue crack or rust hole should be considered a safety warning that the tank is finished and attempting to extend it's service life is setting it up for disaster. Like I said before it makes no difference how skilled the welder is or how good the weld is the tank is STILL seriously compromised.

Quote:

Originally Posted by 65GTO455

If you can't use your brain, you shouldn't be around an air compressor.

It does take someone who knows what they are doing.

If you use your brain you should know better than to attempt to do this and someone who knows what they are doing will not attempt it!

I have an air compressor with a 60 gallon tank. There is a hole about one eighth inch in diameter on the bottom of the tank. I was planning on welding the hole up to repair it.

Is there a better way of doing this, or is this what most of you would do?

I'd buy a new tank
In all likelyhood the tank is rotten. (how old is it?)
If you want to fix it .
Try to just weld the hole up.(if you blow thru it & the hole gets bigger. Then you know it s rotten. If you feel you still want to fix it.
I'd cut the bottom out of it slightly up the sides so you can see inside of it.
If the rest of the tank appears solid AND you're a good experienced welder you could weld in a new bottom. Might be safer to buy a new one and a lot less work.

yep.. if a tank is rusty, replace it.. I had a portable air tank that I could hear rust scale in it... I cut the bung out of it, cleaned it out and turned it into a fuel tank.. couldn't trust it's integrity anymore

heres proof even new tanks can blow.. this is a tank used for air ride suspension from DNA, and it got bad enough DNA had to inform and recall the tanks because it was a manufacturing flaw and happened to others

think about the potential energy that is in the tank.. even a small leak could cause an explosion if the preassure is high enough, simply because of the amount of force the preassure puts on the hole

I'm assuming that this unit is used at home, if not does not matter. YOU repair the tank and later in time something happens and the tank ruptures, thats what they do not explode, what ever dammage that should take place falls on your shoulders!!! Nothing will be covered by home owners/commercial insurance. YOU made unauthorised repairs to a piece of machinary. No insurance co. anywhere will pay off, your taking too much of a chance.

I'd buy a new tank
In all likelyhood the tank is rotten. (how old is it?)
If you want to fix it .
Try to just weld the hole up.(if you blow thru it & the hole gets bigger. Then you know it s rotten. If you feel you still want to fix it.
I'd cut the bottom out of it slightly up the sides so you can see inside of it.
If the rest of the tank appears solid AND you're a good experienced welder you could weld in a new bottom. Might be safer to buy a new one and a lot less work.

That is the kind of thing that causes accidents and could very possibly get someone killed. Think about what you are suggesting, if the tank is rusty and there is a hole in it then obviously the metal is weakened by the rust and will be easy to see. If the tank was cracked instead of rusted and you cut the tank apart as suggested it might look OK inside but is it? If the dang thing is cracked then it is from metal fatigue caused by the repeated expansion and contraction of the tank during normal use and from vibration form the pump/motor. This DID NOT occur only in the small area of the crack and most of the rest tank will have fatigued too but you can't see that! If the crack is welded or, as was also suggested, a patch is welded in then the tank may have that tiny spot strengthened but the rest of the tank will still be dangerous. This entire subject is simply ridiculous, this is a dangerous and irresponsible thing to do that could very well cause an accident that could seriously injure or even kill someone! Fellas even suggesting to someone else to weld on a tank is irresponsible because there is no safe way to do it no matter how good the weld or skilled the welder, the rest of the tank is just as old and nearly as weak as the small spot that failed. Do you guys suggesting this ridiculous approach have any idea how much damage a 60 gallon tank can do? I have no doubt you do not or you would never recommend doing something so darn stupid!

People have been killed in the past and are likely to die from tank explosions in the future, it does happen! There simply is no argument that it does not, there are many documented cases of this happening and as I have said repeatedly I myself have seen two and both had been "repaired". It DOES happen and it CAN happen to you!

I'm assuming that this unit is used at home, if not does not matter. YOU repair the tank and later in time something happens and the tank ruptures, thats what they do not explode, what ever dammage that should take place falls on your shoulders!!! Nothing will be covered by home owners/commercial insurance. YOU made unauthorised repairs to a piece of machinary. No insurance co. anywhere will pay off, your taking too much of a chance.

Of course if they are anywhere near the darn thing then they won't have to worry about it!

OK, this is hotrodman the original poster of the compressor tank leak. Thanks for all the information and advise. I certainly received more information than expected. I have looked inside the tank with a mirror and light and decided the tank has too much rust, the cut off switch was starting to give me trouble, and the unit is 18 years old, so I decided it is not worth fixing. I am going to buy a whole new unit.

1. I want at least the 60 gallon vertical tank design that I had. Two people can get this into a truck and maneuverd into place at the garage. Can any of you recommend one brand over another?

2. The compressor I really wanted was an 80 gallon vertical tank design, but the weight of the unit is close to 500 pounds. Not sure how to get this to the garage and maneuvered into place without hiring a delivery crew? Any ideas?

Will use the compressor at home for all types of body and paint work, pumping up tires, sandblasting, and cleaning parts.

Glad to hear you're going to buy a new one
As has been said it's not a good idea to weld up a tank thats failing
18 years of service is long time !hopefully your new one will last as long

Quote:

Originally Posted by HotRodMan

OK, this is hotrodman the original poster of the compressor tank leak. Thanks for all the information and advise. I certainly received more information than expected. I have looked inside the tank with a mirror and light and decided the tank has too much rust, the cut off switch was starting to give me trouble, and the unit is 18 years old, so I decided it is not worth fixing. I am going to buy a whole new unit.

1. I want at least the 60 gallon vertical tank design that I had. Two people can get this into a truck and maneuverd into place at the garage. Can any of you recommend one brand over another?

2. The compressor I really wanted was an 80 gallon vertical tank design, but the weight of the unit is close to 500 pounds. Not sure how to get this to the garage and maneuvered into place without hiring a delivery crew? Any ideas?

Will use the compressor at home for all types of body and paint work, pumping up tires, sandblasting, and cleaning parts.

Sorry about this thread taking a left turn but honestly the point is exactly what you have arrived at- things do wear out and sometimes need to be replaced! All too often when someone asks a question like you had (very legitimate question BTW) it is too easy for some to sit at a computer and offer advice about something while giving little thought to the possible consequences and the actual size of the endeavor. In this case you were advised to go so far as to cut open an old tank that had already failed, cut out areas of damage, weld patches in place and then weld the whole thing back together! Just think about it, do you REALLY want to be anywhere near a compressor tank with patches on it? I sold and serviced compressors for over thirty years as part of my welding business during which time I have seen many failed tanks, along with the two that actually exploded, and I know from experience just how impractical and dangerous it would be to attempt some of the things suggested here. You made a very wise decision and you will certainly be much safer for it!

BTW, In spite of the common myth tank size has next to nothing to do with compressor performance so if the two compressors you were looking at were comparable in CFM ratings then you did not lose any performance by selecting the compressor with the 60 gallon tank.

Why not look into a new tank and controls. A new tank can't cost as much as a new unit. And your pump/motor is probably in good shape. Chances are the quality of your old pump is much higher than what you can buy now.

This is a good time to work on your welding skills, cut the old tank in two and make a bbq out of it.

An engine hoist is just the ticket fot moving one of those..all you have to do is straddle the compressor with the legs of the hoist..hook it up so you can lift the compressor just enough to clear the floor and roll the whole affair to where you want it..I have moved quite a few heavy articles that way and engine hoists are not just for moving engines..

Sam

__________________
I have tried most all of it and now do what is known to work..

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